The following is from Kadee tech support asking about Kadee's on Life Like cars. I got a fast prompt reply and they were very helpful!
mail@kadee.com
If you wish to use the original trucks then you can use our #28 coupler.
Our 20 series coupler packages contain a special adapter made just for this
type of coupler pocket. Be sure to acquire one of our #205 coupler height
gauges, it is most important to get all of you couplers mounted at the same
height.
Before you insert the "Talgo" adapter check the coupler height because
once the adapter is in place it's very difficult to remove without breaking
something.
To get these Life Like cars to run really good you should add metal
wheels and a bit more weight to each car. A 40 foot car should weigh a bit
less than 4 oz. The NMRA Standards is to start with 1 oz. then add 1/2 oz.
for every actual inch of the cars length. Metal wheels will add weight and
add to the performance. You really do not need to change the trucks until
you learn more about fine tuning each car. Also body mounting couplers
rather than having truck mounted coupler is usually recommended, but again
this should be a later project.